1. Field of the Invention
This invention relates to the field of storage cabinets and, more specifically, to storage cabinets with drawer interlocking mechanisms that prevent the simultaneous opening of more than one cabinet drawer.
2. Description of the Related Art
The benefits of having an interlocking mechanism on a cabinet of drawers which prevents more than one drawer from being opened at the same time has long been recognized. Without such a mechanism, the opening of two drawers could move the center of gravity of the cabinet forward to the point that the cabinet tips over. Because this would most likely occur as a drawer was being opened, the danger of having the cabinet fall forward onto a person opening the drawer is high.
One type of locking system which prevents more than one drawer from being opened at a time uses a vertical, rectangular latch bar at the rear of the cabinet which is pivotable about one of its vertical sides. Each of the drawers has a cam plate affixed to its rear surface. The vertical bar is typically spring-biased such that it remains in one of two angular positions between which it can pivot.
With the cabinet drawers in the closed position, the bar is adjacent to the cam plate of each drawer in a first angular position. As one of the drawers is opened, a camming surface of the cam plate of the drawer being opened engages the vertical bar and pivots it past a centerpoint of its spring bias. This camming action is sufficient to move the bar to a second angular position. In this second position, the bar is still adjacent to the cam plates of the unopened drawers, but physically obstructs the cam plates of the closed drawers such as to prevent their being opened. When the opened drawer is closed, a second camming surface of the cam plate engages the vertical bar and pivots it back to the first angular position, in which the bar no longer obstructs the opening of the other drawers.
Each of the drawers of this prior art cabinet engages the vertical bar in the same manner, such that the opening of any of the drawers results in the pivoting of the bar and the locking of the other drawers. Although this design is somewhat effective, it suffers from some problematic side effects. Because the vertical bar is the element which must restrict the opening of the locked drawers, it is necessary to make it sturdy enough to resist the force of someone yanking on a locked drawer. In addition, because the bar must be free to pivot along its entire length, it is generally connected only at the top and bottom of the cabinet. Thus, for a relatively large cabinet, the bar may be up to six feet long, and must resist lateral forces from the drawers with support only at its two ends. For this reason, the bar is made out of a relatively high-gauge metal, typically steel.
Because the locking bar described above is made of a heavy, sturdy material, it has a significant amount of inertia. As a result, a problem occurs when one of the cabinet drawers is slammed shut. The slamming of the drawer causes the cam plate of the open drawer to strike the vertical bar with a great deal of force which, in turn, causes the bar to pivot with a relatively high angular velocity. When the bar reaches the second pivot position, the inertia of the heavy bar causes it to bounce back against the force of the spring bias. If the drawer is slammed hard enough, the bar bounces back to the position typically occupied only when one of the drawers is opened. Instead, however, the drawer which was slammed shut is in the closed position, along with the others, and the position of the bar obstructs the cam plates of all of the drawers, preventing any of them from being opened.
The "lock-up" situation described above is a problem which has plagued cabinets which use this type of design. In a cabinet which also has a key lock, this "lock-up" situation can be remedied by turning the key in the lock to return the bar to its unlocked position. However, if the key happens to be in one of the drawers, as is often the case, or is otherwise unavailable, a cabinet owner who suffers from this problem must wait for a trained service person to travel to the site of the cabinet and correct the problem. In the interim, materials inside the cabinet drawers are inaccessible. Because of the risk of this problem, there has been reluctance to use this type of cabinet design for industries where access to the contents of the drawers may be of critical importance, such as the medical industry.